Implement source debugging for interpreter and AOT (#769)

Implement source debugging feature for classic interpreter and AOT:
- use `cmake -DWAMR_BUILD_DEBUG_INTERP=1` to enable interpreter debugging
- use `cmake -DWAMR_BUILD_DEBUG_AOT=1` to enable AOT debugging

See doc/source_debugging.md for more details.

core/iwasm/libraries/debug-engine/debug_engine.cmake

@@ -0,0 +1,12 @@
+# Copyright (C) 2021 Ant Group.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+set (DEBUG_ENGINE_DIR ${CMAKE_CURRENT_LIST_DIR})
+
+add_definitions (-DWASM_ENABLE_DEBUG_INTERP=1)
+
+include_directories(${DEBUG_ENGINE_DIR})
+
+file (GLOB source_all ${DEBUG_ENGINE_DIR}/*.c)
+
+set (DEBUG_ENGINE_SOURCE ${source_all})